New, cleaner package repository structure.

Package repositories now look like this:

    top-level-dir/
        repo.yaml
        packages/
            libelf/
                package.py
            mpich/
                package.py
            ...

This leaves room at the top level for additional metadata, source,
per-repo configs, indexes, etc., and it makes it easy to see that
something is a spack repo (just look for repo.yaml and packages).

var/spack/repos/builtin/packages/py-basemap/package.py

@@ -0,0 +1,20 @@
+from spack import *
+import os
+
+class PyBasemap(Package):
+    """The matplotlib basemap toolkit is a library for plotting 2D data on maps in Python."""
+    homepage = "http://matplotlib.org/basemap/"
+    url      = "https://downloads.sourceforge.net/project/matplotlib/matplotlib-toolkits/basemap-1.0.7/basemap-1.0.7.tar.gz"
+
+    version('1.0.7', '48c0557ced9e2c6e440b28b3caff2de8')
+
+    extends('python')
+    depends_on('py-setuptools')
+    depends_on('py-numpy')
+    depends_on('py-matplotlib')
+    depends_on('py-pil')
+    depends_on("geos")
+
+    def install(self, spec, prefix):
+        env['GEOS_DIR'] = spec['geos'].prefix
+        python('setup.py', 'install', '--prefix=%s' % prefix)